The present invention relates to an apparatus and a process for checking/separating out cigarettes.
In the packaging of cigarettes, these are guided, stacked on top of one another in a vertical shaft, to an apparatus forming blocks of cigarettes which comprise a number of cigarettes corresponding to the pack content. The shaft is therefore divided into several (for example, 7) individual shafts. To ensure that the (closed) pack does not contain a defective cigarette, that is to say one from which tobacco has fallen out during transport, the cigarettes in the assembled block are tested by mechanical sensing means and an entire block is rejected even when only one of the cigarettes is defective. This means that a whole series of intact cigarettes has to be rejected, although often only a single cigarette is defective.
In order to reduce the reject rate, it is known, for example from German Auslegeschrift 1,257,651, to test and reject individual cigarettes before these have been formed into blocks and pushed into a box. Here, the defective cigarettes are ejected from the continuous flow by being blown out. According to this publication, the error check is carried out by means of mechanical sensing. However, this mechanical sensing is relatively slow.
German Auslegeschrift 1,532,268 makes known a contactless sensing, in which the cigarettes are guided past a reflection-light barrier arrangement with their tobacco-side ends sliding on a transparent plate. After the cigarettes have been guided by means of the plate in a specific relative position as regards the light barrier arrangement, it is possible to ascertain from the output signal of the light barrier whether there is a cavity in the tobacco filling at the end or whether it is "level" with the end face. However, since such a check involves relatively small changes in the output signal from the light barrier, the cigarettes must rest exactly on the transparent surface. As soon as there is a certain distance between the surface and the cigarette end, the output signal from the light barrier changes and the cigarette is detected as defective, even though there is actually no fault. Moreover, this exact guidance on the one hand reduces the maximum possible working speed of the arrangement as a whole because of the frictional forces occurring and, on the other hand, increases the danger that the cigarettes will jam or be damaged in the (vertical) shaft, since the cigarettes have to be guided without any play.